Method and system for HARQ operation and scheduling in joint TDD and FDD carrier aggregation

ABSTRACT

A method at a user equipment for hybrid automatic repeat request (HARQ) operation, the user equipment operating on a primary carrier having a first duplex mode and on at least one secondary carrier having a second duplex mode, the method using HARQ timing of the first duplex mode if the timing of the first duplex mode promotes acknowledgement opportunities over using HARQ timing of the second duplex mode; and using HARQ timing of the second duplex mode if the timing of the second duplex mode promotes acknowledgement opportunities over using HARQ timing of the first duplex mode.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation and claims priority to U.S.Non-Provisional application Ser. No. 14/033,256, filed Sep. 20, 2013,the entire contents of which is hereby expressly incorporated byreference herein in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to hybrid automatic repeat request (HARQ)operation and scheduling in carrier aggregation, and in particularrelates to HARQ operation and scheduling in carrier aggregation systemsusing combined frequency division duplex (FDD) and time division duplex(TDD) modes.

BACKGROUND

In the 3^(rd) Generation Partnership Project (3GPP) Long Term Evolution(LTE) Architecture, downlink and uplink transmissions are organized intoone of two duplex modes. These modes are frequency division duplex modeand a time division duplex mode. Frequency division duplex mode usespaired spectrum to separate the uplink and downlink transmissions whilethe TDD mode uses a common spectrum and relies on time multiplexing toseparate uplink and downlink transmissions.

With FDD, the acknowledgement for a transmission typically occurs a setnumber of subframes after the transmission has been received. Forexample, in many systems the acknowledgement is sent back to the networkfrom the user equipment (UE) four subframes after receipt of thetransmission. In TDD, depending on the TDD mode, the HARQ feedback issent in a predefined manner to the network once a transmission isreceived.

In order to increase data throughput, carrier aggregation may beutilized in LTE-advanced systems. To support 3GPP carrier aggregation, aLTE-advanced UE may simultaneously receive or transmit on one ofmultiple component carriers. In some cases, component carriers utilizethe same duplex mode, and the HARQ operation and scheduling of thecomponent carriers is therefore relatively straightforward. However, insome cases a secondary component carrier may be operating in a differentduplex mode than a primary component carrier. In this case, the HARQoperation and scheduling are currently undefined.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will be better understood with reference to thedrawings, in which:

FIG. 1 a graph showing an example of uplink and downlink subframes in afrequency division duplex mode;

FIG. 2 is a graph showing an example of uplink and downlink subframes ina time division duplex mode;

FIG. 3 is a timing diagram showing HARQ operation on a secondary FDDcarrier with a primary carrier in TDD mode utilizing FDD PDSCH HARQtiming;

FIG. 4 is a timing diagram showing PDSCH HARQ and scheduling timing of asecondary FDD carrier from a primary carrier in TDD mode;

FIG. 5 is a timing diagram showing PUSCH HARQ and scheduling timing of asecondary FDD carrier from a primary carrier in TDD mode;

FIG. 6 is a timing diagram showing a secondary FDD carrier utilizing theTDD configuration PDSCH HARQ timing of the primary cell;

FIG. 7 is a timing diagram showing HARQ operation on a secondary FDDcarrier with a primary TDD carrier utilizing FDD PDSCH HARQ timing;

FIG. 8 is a flow diagram showing selection of HARQ timing operation on asecondary carrier;

FIG. 9 is a timing diagram showing a secondary FDD carrier utilizing TDDconfiguration 2 timing for HARQ operation for a primary carrier having 5ms periodicity;

FIG. 10 is a timing diagram showing a secondary FDD carrier utilizingTDD configuration 5 timing for HARQ operation for a primary carrierhaving 10 ms periodicity;

FIG. 11 is a flow diagram showing a selection of a TDD configuration forHARQ operation on a secondary carrier;

FIG. 12 is a timing diagram showing a secondary FDD carrier utilizingTDD configuration 5 timing for HARQ operation;

FIG. 13 is a timing diagram showing HARQ operation on a secondary FDDcarrier utilizing a next available subframe on a primary TDD carrier;

FIG. 14 is a timing diagram showing cross carrier scheduling from aprimary TDD carrier for a secondary FDD carrier;

FIG. 15 is a block diagram showing a bitmap for use with cross carrierscheduling;

FIG. 16 is a timing diagram showing a timing scheme of PUSCH HARQ of asecondary FDD carrier for cross carrier scheduling from a TDD carrier;

FIG. 17 is a simplified block diagram of an example network element; and

FIG. 18 is a block diagram of an example user equipment.

DETAILED DESCRIPTION OF THE DRAWINGS

The present disclosure provides a method at a user equipment for hybridautomatic repeat request (HARQ) operation, the user equipment operatingon a primary carrier having a first duplex mode and on at least onesecondary carrier having a second duplex mode, the method comprising:using HARQ timing of the first duplex mode if the timing of the firstduplex mode promotes acknowledgement opportunities over using HARQtiming of the second duplex mode; and using HARQ timing of the secondduplex mode if the timing of the second duplex mode promotesacknowledgement opportunities over using HARQ timing of the first duplexmode.

The present disclosure further provides a user equipment for hybridautomatic repeat request (HARQ) operation, the user equipment operatingon a primary carrier having a first duplex mode and on at least onesecondary carrier having a second duplex mode, the user equipmentcomprising a processor configured to: use HARQ timing of the firstduplex mode if the timing of the first duplex mode promotesacknowledgement opportunities over using HARQ timing of the secondduplex mode; and use HARQ timing of the second duplex mode if the timingof the second duplex mode promotes acknowledgement opportunities overusing HARQ timing of the first duplex mode.

In an LTE system, downlink and uplink transmissions are organized intoone of two duplex modes, namely FDD and TDD modes. FDD mode uses pairedspectrum to separate the uplink and downlink transmissions, while in TDDmode, common spectrum is used and the mode relies on time multiplexingto separate uplink and downlink transmissions.

While the present disclosure is described below with regard to 3^(rd)Generation Partnership Project (3GPP) Long Term Evolution NetworkArchitecture, the present disclosure is not limited to LTE. Othernetwork architectures including a TDD mode and an FDD mode may alsoutilize the HARQ operation and scheduling embodiments described herein.

Reference is now made to FIG. 1, which shows downlink and uplinktransmissions for an FDD mode. In particular, the embodiment of FIG. 1has a first channel 110 and a second channel 112. Channel 110 is usedfor uplink subframes 120, while channel 112 is used for downlinksubframes 122.

Referring to FIG. 2, a time division duplex system is shown having onlyone channel 210, where the downlink and uplink subframes are duplexedtogether on the channel. In particular, in the embodiment of FIG. 2,downlink subframes 220 and 222 are interspersed with uplink subframes230 and 232.

While the embodiment of FIG. 2 shows an alternation between uplink anddownlink subframes, other configurations are possible. Specifically, ina 3GPP LTE TDD system, a subframe of a radio frame can be a downlink, anuplink, or a special subframe. The special subframe comprises downlinkand uplink time regions separated by a guard period to facilitatedownlink to uplink switching. In particular, each special subframeincludes three parts: a downlink pilot time slot (DwPTS), an uplinkpilot time slot (UpPTS) and a guard period (GP). Physical downlinkshared channel (PDSCH) transmissions may be made in a downlink subframeor in the DwPTS portion of a special subframe.

The 3GPP Technical Specification (TS) 36.211, “Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation”,v.11.0.0, Sep. 19, 2012, the contents of which are incorporated hereinby reference, defines seven different uplink/downlink configurationschemes in LTE TDD operations. These are shown below with regard toTable 1.

TABLE 1 LTE TDD Uplink-Downlink Configurations Downlink-to- Uplink-Uplink downlink Switch-point Subframe number configuration periodicity 01 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U U U 1  5 ms D S U U D D S U UD 2  5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S UU D D D D D D 5 10 ms D S U D D D D D D D 6  5 ms D S U U U D S U U D

In Table 1 above, the “D” is for a downlink subframe, the “U” is foruplink subframes, and the “S” is for special subframes.

Thus, as shown in Table 1 above, there are two switching pointperiodicities specified in the LTE standard for TDD. They are 5 ms and10 ms, of which the 5 ms switching point periodicity is introduced tosupport the co-existence between LTE and low chip rate universalterrestrial radio access (UTRA) TDD systems. The 10 ms switching pointperiodicity is for the coexistence between LTE and a high chip rate UTRATDD system.

The seven UL/DL configurations of Table 1 cover a wide range ofuplink/downlink allocations, ranging from downlink heavy 1:9 ratio inconfiguration 5 to UL heavy 3:2 ratio in configuration 0.

Based on the configurations, as compared to FDD systems, TDD systemshave more flexibility in terms of the proportion of resources assignableto uplink and downlink communications within a given assignment ofspectrum. In other words, TDD systems can distribute the radio resourcesunevenly between the uplink and the downlink, enabling potentially moreefficient radio resource utilization by selecting an appropriateuplink/downlink configuration based on interference situations anddifferent traffic characteristics in the uplink and downlink.

HARQ provides an acknowledgement or a negative acknowledgement of thereception of a data transmission. In an LTE FDD system, the UE andevolved node B (eNB) processing times for both the downlink and uplinkreceipt are fixed because of the continuous downlink and uplinktransmission and reception and invariant downlink and uplink subframeconfiguration. In particular, the UE, upon detection on a given servingcell of a physical downlink control channel (PDCCH) with a downlinkcontrol information (DCI) format 0/4 and/or a physical HARQ indicationchannel (PHICH) transmission in subframe n intended for the UE, adjuststhe corresponding physical uplink shared channel (PUSCH) transmission insubframe n+4 according to the PDCCH and PHICH information.

On the downlink, the UE, upon detection of the PDSCH transmission insubframe n−4 intended for the UE and for which an HARQ-acknowledgementis provided, transmits the HARQ acknowledgement response in subframe n.

Conversely, in a TDD system, since the uplink and downlink transmissionsare not continuous, such that the transmissions do not occur in everysubframe, the scheduling and HARQ timing relationships are separatelydefined in the LTE specifications.

Currently, the HARQ ACK/NACK timing relationship for the downlink isdefined by Table 10.1.3.1-1 in the 3GPP TS 36.213, “3rd GenerationPartnership Project; Technical Specification Group Radio Access Network;Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layerprocedures (Release 11)”, v. 11.3.0, June 2013, the contents of whichare incorporated herein by reference. The table is reproduced in Table 2below.

In Table 2, an association is made between an uplink subframe n, whichconveys the ACK/NACK, with downlink subframes n−k_(i), i=0 to M−1. Forexample, with uplink/downlink TDD configuration 0, subframe 2 willconvey an ACK/NACK bit for the PDSCH on subframe 6.

TABLE 2 Downlink Association Set Index K: {k₀, k₁, . . . k_(M−1)} UL-DLSubframe n configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 — 4 — — 6 — 4 1 — —7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7, — — 4, 6 3 — — 7,6, 11 6, 5 5, 4 — — — — — 4 — — 12, 8, 7, 11 6, 5, — — — — — — 4, 7 5 —— 13, 12, 9, 8, — — — — — — — 7, 5, 4, 11, 6 6 — — 7 7 5 — — 7 7 —

Further, in 3GPP TS 36.213, Table 8.3-1, which is shown below withregard to Table 3, indicates that the PHICH ACK/NACK received in adownlink sub-frame i is linked with the uplink data transmission in theuplink subframe i−k, where k is given in Table 3. For example, with theuplink/downlink TDD configuration 1, subframe 1 conveys the ACK/NACK bitfor the PUSCH on subframe 7 (i=1, k=4 from Table 3 below, thusi−k=subframe 7). Additionally, for the uplink/downlink configuration 0,in subframes 0 and 5, when the I_(PHICH)=1, k=6. This is because theremay be two ACK/NACKs for a UE transmitted on the PHICH in subframes 0and 5, one being represented by I_(PHICH)=1 and the other byI_(PHICH)=0.

TABLE 3 k for HARQ ACK/NACK TDD UL-DL Subframe number i configuration 01 2 3 4 5 6 7 8 9 0 7 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 46

The uplink grant, ACK/NACK and transmission/retransmission relationshipprovided below with regard to Table 4. Table 4 represents Table 8.2 ofthe 3GPP TS 36.213 Technical Specification.

TABLE 4 k for PUSCH transmission TDD UL-DL Subframe number nconfiguration 0 1 2 3 4 5 6 7 8 9 0 4 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 44 5 4 6 7 7 7 7 5

In Table 4, the UE, upon detection of a PDCCH with DCI format 0/4 and/ora PHICH transmission in subframe n intended for the UE, adjusts thecorresponding PUSCH transmission in sub-frame n+k, where k is given inthe table.

For example, for TDD uplink/downlink configuration 0, if the leastsignificant bit (LSB) of the uplink index in the DCI format 0/4 is setto 1 in sub-frame n or a PHICH is received in sub-frame n=0 or 5 in theresource corresponding to I_(PHICH)=1, or the PHICH is received insub-frame n=1 or 6, the UE may adjust the corresponding PUSCHtransmission in sub-frame n+7.

If, for TDD uplink/downlink configuration 0, both the most significantbit and least significant bit of the UL index in the DCI format 0/4 areset in sub-frame n, the UE may adjust the corresponding PUSCHtransmission in both sub-frames n+k and n+7, where k is given by Table4.

As seen above, both grant and HARQ timing linkage in TDD are morecomplicated than the fixed time linkages used in LTE FDD systems.

Carrier Aggregation

To meet the need of rapidly growing UE throughput, a maximum of 100 MHzbandwidth is specified for the LTE-advanced systems. Carrier aggregationenables multiple component carriers, which use up to 20 MHz bandwidth,to be aggregated to form a wider total bandwidth.

To support 3GPP carrier aggregation, in LTE-A, a UE may simultaneouslyreceive or transmit on one or multiple component carriers (CCs).Multiple CCs could be from the same eNB or from different eNBs. In anFDD system, the number of CCs aggregated in the downlink could bedifferent from that in the uplink.

For CA, there is one independent hybrid-ARQ entity per serving cell ineach of the uplink or downlink. Multiple aggregated cells (carriers) usemultiple HARQ entities. However, each UE has only one radio resourcecontrol (RRC) connection with the network.

The serving cell handling the RRC connection establishment orre-establishment or handover is referred to as the Primary Cell (PCell).The carrier corresponding to the PCell in the downlink is termed thedownlink primary component carrier (DL PCC) while in the uplink theuplink primary component carrier (UL PCC).

Other serving cells are referred to as secondary cells (SCells) andtheir corresponding carriers are referred to as secondary componentcarriers (SCC).

The carriers may be aggregated intra-band, such that they use the sameoperational band, and/or inter-band, where a different operational bandis used.

The configured serving cell set for a UE consists of one PCell and oneor more SCells.

Cross Carrier Scheduling

In addition to the normal carrier self-scheduling in Release 8 or 9 ofthe LTE specifications, cross-carrier scheduling is also possible. APDCCH on one carrier can relate to data on the PDSCH or PUSCH of anothercarrier. Self-scheduling means that the shared data channel, PDSCH orPUSCH, of a carrier is scheduled by the PDCCH which is transmitted onthe same carrier, while cross-scheduling means that the shared datachannel, PDSCH or PUSCH, of a carrier is scheduled by the PDCCH which istransmitted on another carrier.

For carrier aggregation, information on the component carriers that a UEneeds to monitor is notified by the eNB via MAC and RRC messaging. Thismay help reduce the UE's power consumption as the UE only needs tomonitor the component carriers configured for possible schedulinginformation.

For a UE monitoring more than one component carrier, the schedulinginformation for each subframe is sent on a scheduling carrier. Inparticular, the scheduling carrier could be a PCell or SCell. However,the PCell can only be scheduled by the PCell itself.

Further, the PUCCH is only allowed to be transmitted on the PCell. Thisis the same for FDD and TDD systems.

For uplink grants, after demodulation of PUSCH, the corresponding uplinkACK or NACK is carried by the PHICH, which is transmitted from thescheduling carrier. This is the same for FDD and TDD systems.

In 3GPP TS36.331, “3rd Generation Partnership Project; TechnicalSpecification Group Radio Access Network; Evolved Universal TerrestrialRadio Access (E-UTRA); Radio Resource Control (RRC); Protocolspecification (Release 11)”, v. 11.4.0, June 2013, the contents of whichare incorporated herein by reference, networks can send an RRCconfiguration message containing a CrossCarrierSchedulingConfiginformation element (IE) to further configure the cross-carrierscheduling. The CrossCarrierSchedulingConfig IE includes at least thefollowing fields:

-   -   a. schedulingCellID: to notify a UE where (at which        cell/carrier) to monitor the PDCCH (self-scheduling or        cross-carrier scheduling).    -   b. pdsch-Start: the starting OFDM symbol of PDSCH for the        concerned SCell. Values 1, 2, 3 are applicable when dl-Bandwidth        for the concerned SCell is greater than 10 resource blocks,        values 2, 3, 4 are applicable when dl-Bandwidth for the        concerned SCell is less than or equal to 10 resource blocks.        This can be treated as a virtual PCFICH.

The activation/deactivation of component carriers is done via MACcontrol elements. As a result, a UE with cross-carrier scheduling andwith more than one carrier activated needs only to monitor the PDCCH onthe scheduling cell. In other words, there is no need to monitor thePDCCH on the scheduled cell and there is no need to detect the physicalcontrol format indicator channel (PCFICH) to derive the starting symbolof the PDSCH for the scheduled cell.

Regarding the above, although the current LTE specifications can operatein two different duplex modes, it is unclear how a device would operatejointly between an FDD and a TDD duplex mode. Specifically, the use ofcombined FDD/TDD joint operation enables effective use of reallocatedspectrum through a combination of two duplex modes. For example, a firstdeployment scenario of TDD/FDD joint operation may be by carrieraggregation. This supports either TDD or FDD as the primary cell. Giventhe fact that the current HARQ operation is defined separately for TDDand FDD modes, and since they are largely different, the use of HARQoperations will run into some issues when two modes are jointlyoperated.

With regard to HARQ timing and scheduling issues, the variousembodiments below are described with regard to the TDD carrier beingconfigured as the primary cell and an FDD carrier being a secondarycell. However, this is not limiting and the embodiments described hereincould equally be used with the FDD being the primary carrier.

Reference is now made to FIG. 3. As indicated above, only one PUCCHexists and is configured at the primary carrier. Thus HARQ for secondarycarriers proceeds through the primary carrier.

FIG. 3 shows a self-scheduling case of PDSCH HARQ timing where a TDDprimary carrier 310 with configuration 1 is aggregated with an FDDsecondary carrier 320.

As seen in FIG. 3, the FDD uses self-scheduling ACKs, which are providedin four subframes from the received downlink transmission. Thus, the FDDcarrier follows the existing FDD timing rules of the PDSCH HARQ-ACK. Inthe embodiment of FIG. 3, the PDSCH transmitted on subframes 0, 1, 2, 5,6 and 7 cannot be properly acknowledged as shown by arrows 330 if usingthe PUCCH, due to the lack of an uplink subframe on the TDD primarycarrier.

Further, referring to FIG. 4, for the same carrier aggregation case withcross-carrier scheduling, where the PDCCH on one carrier relates to dataon another carrier, the PDSCH scheduling and HARQ timing is illustratedfor such cross-carrier scheduling.

In particular, the primary carrier 410 operates in a TDD mode(configuration 1), whereas the secondary carrier 420 operates in an FDDmode. The scheduling is shown for example with references 430, 432, 434,436.

As seen in FIG. 4, since subframes 2 and 3 on the primary carrier 410are uplink subframes, subframes 2 and 3 on the FDD secondary carrier 420cannot be scheduled.

In the embodiment of FIG. 4, the TDD is in configuration 1 and thereforesubframes 2, 3, 7 and 8 cannot be cross-carrier scheduled.

The HARQ timing, shown for example with line 440 for HARQ on thesecondary carrier 420 in subframe 9, may work properly for the subframesthat are scheduled utilizing the TDD configuration for HARQ.

Similarly for the uplink, with FDD PUSCH and cross-carrier schedulingfrom a TDD carrier, the TDD PUSCH scheduling timing can only be used forsubframes 1, 4, 6 and 9, as shown in FIG. 5.

In FIG. 5, the TDD configured carrier is the primary carrier 510 and theFDD configured carrier is the secondary carrier 520. As seen in FIG. 5,only subframes 1, 4, 6 and 9 may be used to schedule (6, 4, 6, 4subframes later as in Table 4 above), therefore allowing only uplinksubframes 2, 3, 7 and 8 to be cross-carrier scheduled from the TDDcarrier. All other uplink subframes on the FDD carrier would becomeunusable for the UE.

In accordance with the above, various embodiments are provided below toovercome the HARQ operations and scheduling issues.

PDSCH HARQ-ACK Embodiments

Flexible PDSCH HARQ-ACK Timing

In accordance with one embodiment of the present disclosure, existingPDSCH HARQ-ACK timing may be fully reused for both TDD and FDD modes. Nonew PDSCH HARQ-ACK timing is required and the embodiment is applicableto both self and cross-carrier scheduling.

In particular, when a PCell is TDD and SCell is FDD, for the TDDcarrier, the PDSCH HARQ-ACK timing follows timing corresponding to itsown uplink/downlink TDD configuration. The PDSCH HARQ timing of the FDDcarrier follows the reference timing. The reference timing is determinedbased on the primary cell TDD uplink/downlink configuration.

In particular, reference is now made to FIG. 6 in which primary cell 610has a TDD configuration and secondary cell 620 has an FDD configuration.As seen in the embodiment of FIG. 6, the frames on the FDD carrier 620that correspond with downlink or special subframes of TDD carrier 610utilize the same HARQ timing. In other words, the subframes on FDDcarrier 620 utilize the TDD configuration 1 timing for the subframescorresponding to downlink or special subframes.

Thus, as shown by arrows 630, the ACKs/NACKs are provided in thesubframe corresponding to the configuration 1 timing. Thus, for subframe0, the acknowledgement is provided in subframe 7 on the uplink for theTDD configuration 1. Similarly, subframe 1 is acknowledged on subframe 7and subframe 4 is acknowledged on subframe 8.

In accordance with this embodiment, subframes 2, 3, 7 and 8 will not beable to be acknowledged.

The above may be therefore more useful when the PCell configuration isdownlink subframe heavy. As will be appreciated by those in the art,when the TDD configuration is uplink heavy, a significant number ofdownlink subframes on the FDD carrier will be unusable.

Thus, with the embodiment of FIG. 6, the majority of the downlink PDSCHsare able to be properly acknowledged or negatively acknowledged, leavinga small portion of PDSCHs which do not have ACK/NACK linkage. In thiscase, the eNB may simply pass the ACK to a higher layer and let the RRChandle the package error.

When comparing the embodiment of FIG. 6 with that of only following FDDtiming, the above is able to acknowledge 60% of the of the PDSCHdownlink subframes, while only 40% of the PDSCH subframes can beacknowledged or negatively acknowledged when following FDD timing.

On the other hand, when the primary cell TDD configuration is uplinksubframe heavy, the reference timing may, in one embodiment, utilize theFDD PDSCH HARQ timing. Reference is now made to FIG. 7, which shows anexample of FDD PDSCH HARQ timing using the TDD configuration 0 asprimary cell. In accordance with Table 1 above, the configuration 0 isuplink subframe heavy with a ratio of 3:2.

In particular, the primary cell 710 is a TDD configuration 0 and thesecondary cell 720 is an FDD configuration. As seen by arrows 730, theconfiguration allows subframes 3, 4, 5 and 8, 9, 0 to be acknowledgedfour subframes later.

In the example of FIG. 7, 60% of the PDSCHs are able to be properlyacknowledged by following the FDD timing and 40% of the PDSCHs are notable to have an acknowledgement linkage.

Thus, in accordance with FIGS. 6 and 7, a decision can be made based onthe configuration of the TDD at the primary cell as to which embodimentto use. The decision may be based on the efficiency of the HARQtechnique, and the selection of whichever is more efficient is made. Inthe case where it is equally efficient to use either technique, (e.g. ifthe number of uplink subframes is the same as the number of downlinksubframes in the TDD configuration of the primary cell), either the TDDconfiguration of the primary cell or the FDD HARQ timing can beconsidered as the reference timing.

Reference is now made to FIG. 8, which shows a process diagram of theabove. In particular, the process of FIG. 8 starts at block 810 andproceeds to block 820 in which a precondition is that a TDD primary cellis aggregated with FDD secondary cells.

The process then proceeds to block 830 in which a check is made todetermine whether it is more efficient to use TDD timing or FDD timing.For example, the determination for each of the secondary cells may bewhether the number of uplink subframes is greater than the number ofdownlink subframes in the primary cell TDD configuration.

From block 830, if the TDD configuration is less efficient, the processproceeds to block 832 in which the FDD PDSCH timing is used, as shown inFIG. 7 above.

Conversely, if the TDD configuration is more efficient, for example ifthe number of DL subframes exceeds the number of UL subframes, theprocess proceeds from block 830 to block 840 in which the primary cellTDD PDSCH timing is utilized for the acknowledgements, as shown abovewith regards to FIG. 6.

If it is equally efficient to use either timing, for example if thenumber of uplink subframes and the number of downlink subframes areequal, then either the PCell TDD or the FDD PDSCH timing may beutilized. The choice may be specified for example in various standardsor made by the carrier to a UE. In this case the process proceeds toblock 850.

From blocks 832, 840 or 850, the process proceeds to block 860 and ends.

In one embodiment, the selection of the PDSCH HARQ timing may be handledby higher layer signalling. For example, the selection of the PDSCH HARQtiming may be embedded in the RRC reconfiguration message when the FDDSCell is added to the primary TDD carrier. In another example, theselection of the PDSCH HARQ timing may be embedded in a MAC controlelements signalled to the UE.

Switching Periodicity Based Embodiment

In a further embodiment, the FDD secondary cell may be provided with aTDD uplink/downlink configuration utilizing a specific TDDconfiguration, regardless of the actual TDD configuration of the primarycell. In particular, the reference timing can follow TDD uplink/downlinkconfiguration 2 from Table 1 above if the primary cell TDD configurationswitching periodicity is 5 ms and timing may follow TDD uplink/downlinkconfiguration 5 for switching periodicity of 10 ms.

Reference is now made to FIG. 9, which shows an example of the timingmethod with a TDD configuration 1 as the primary cell.

In particular, as seen in FIG. 9, the primary cell 910 has TDDconfiguration 1 whereas the secondary cell 920 has an FDD configuration.

From Table 1 above, utilizing configuration 2 with a 5 ms periodicity,the uplink subframes are in subframes 2 and 7, which are used to providethe HARQ feedback. Thus, referring to FIG. 9, as shown by arrows 930,subframes 4, 5, 6 and 8 utilize subframe 2 in the next frame for theHARQ feedback. Similarly, subframes 9, 0, 1 and 3 utilize subframe 7 forthe HARQ feedback.

FIG. 9 therefore shows an example where 80% of the PDSCH subframes canbe properly acknowledged.

When the TDD switching periodicity is 10 ms, TDD configuration 5 PDSCHHARQ timing is used. From Table 1, configuration 5 only has one uplinksubframe and thus the ability of the ACK/NACK is increased to 90%.

In particular, reference is made to FIG. 10 which shows an example ofthe timing method with a TDD configuration 3 as the primary cell 1010.The secondary cell 1020 has an FDD configuration. As TDD configuration 3has a 10 ms periodicity, the TDD configuration 5 PDSCH HARQ timing isused.

Thus, as seen in FIG. 10, every subframe (except subframe 2) usessubframe 2 of the primary cell for acknowledgement. The acknowledgement,as with all embodiments herein, must be delayed by a minimum processingtime, for example 4 subframes, and thus for subframes 9, 0 and 1 theacknowledgement waits until subframe 2 in a subsequent frame for theacknowledgement. The acknowledgements are shown with arrows 1030 in theexample of FIG. 10.

A process at a user equipment to determine which of the embodiments ofFIGS. 9 and 10 above to use is provided with regard to FIG. 11. Inparticular, the process of FIG. 11 starts at block 1110 and proceeds toblock 1120 in which a precondition is at a TDD primary cell isaggregated with FDD secondary cells.

The process then proceeds to block 1130 in which a determination is madewhether the switching periodicity is 5 ms or 10 ms. From block 1130, ifthe periodicity is 5 ms the process proceeds to block 1135 in which TDDconfiguration 2 is used on the secondary cell for the PDSCH ACK timing.

Conversely, from block 1130 if the periodicity is 10 ms then the processproceeds to block 1140 in which the TDD configuration 5 PDSCH timing isutilized.

From blocks 1135 and 1140 the process proceeds to block 1150 and ends.

In a further alternative embodiment, the timing for TDD configuration 5PDSCH HARQ may be used regardless of the TDD switching periodicity.

Reference is now made to FIG. 12, which illustrates one example of thealternative embodiment. In particular, the primary cell has a TDDconfiguration 1, as shown by reference numeral 1210 and the secondarycell 1220 has an FDD downlink configuration.

The example of FIG. 12 shows, using arrows 1230, that every subframebesides subframe 2 is able to provide ACK/NACK feedback on the subframe2 of the primary cell.

From FIG. 12, the specific TDD configuration for the primary cell isirrelevant as all current TDD configurations have an uplink subframe atsubframe 2.

ACK/NACK on Next Available Uplink Subframe

In a further embodiment, an ACK or NACK may be provided on all downlinkPDSCH transmissions on every possible downlink subframe of the secondarycarrier. This embodiment provides a way of transmitting the ACK/NACKbits on the next available TDD uplink subframe for the FDD PDSCHsubframe that does not have a linked uplink subframe for an ACK/NACKtransmission according to existing FDD PDSCH HARQ-ACK timing. In anotherembodiment, the next available rule may be specified in the standards,e.g. in a tabular form.

However, the processing delay still needs to be taken into considerationand thus the next available uplink subframe must be at least foursubframes after the current one in one embodiment.

Reference is now made to FIG. 13, which shows an example of theembodiment. In the embodiment of FIG. 13, primary cell 1310 has a TDDconfiguration 1 whereas the secondary cell 1320 has an FDDconfiguration. In FIG. 13, as shown by arrows 1330, uplink subframe 7provides acknowledgements for subframes 0, 1, 2 and 3.

Further, in the embodiment of FIG. 13, uplink subframe 8 is used toacknowledge subframe 4 and subframe 2 is used to acknowledge subframes5, 6, 7, and 8. Subframe 3 is used to acknowledge subframe 9.

An eNB may decode the ACK or NACK for a corresponding FDD PDSCH based onthe next availability rule above. In particular, the eNB would know thatsubframes 0, 1, 2 and 3 would provide their acknowledgement on subframe7 as the eNB knows the TDD configuration of the UE. Similarly, the eNBwould know where the remaining subframes provide their acknowledgments.

Balanced Load of ACK/NACK Bits

In a further alternative embodiment to the ACK/NACK on the nextavailable uplink subframe, the distributing the ACK/NACK bits amongavailable TDD uplink subframes to achieve a more balanced and optimaluse of physical uplink controlled channel resources is provided. Suchacknowledgements may be implemented utilizing a look-up table, forexample.

In the present embodiment, the ACK/NACK bits may be spread to distributethem more evenly while keeping the change to the existing scheme assmall as possible.

Currently, TDD HARQ ACK/NACK timing relationships for downlinks aredefined by Section 10.1.3.1-1 of the 3GPP TS 36.213 Specificationprovided above. Table 2 above may be modified to accommodate theprovision of ACK/NACK bits for PDSCH transmitted on a FDD carrier and isshown below with regard to Table 5.

TABLE 5 Downlink Association Set Index K: {k₀, k₁, . . . k_(M−1)} UL- DLSubframe n config. 0 1 2 3 4 5 6 7 8 9 0 — — 6 5, 6 4, 5 — — 6 5, 6 4, 51 — — 7, 6 4, 5, 6 — — — 7, 6 4, 5, 6 2 — — 8, 7, 4, — — — — 8, 7, 4, —— 6, 5 6, 5 3 — — 11, 10, 6, 7, 5, 4, — — — — — 9, 8 8 6 4 — — 12, 8, 6,5, — — — — — — 11, 10, 4, 7, 9 8 5 — — 13, 12, — — — — — — — 9, 8, 7, 5,4, 11, 6, 10 6 — — 7, 8 7, 6 5, 6 — — 5, 6 5, 6 —

Table 5 is only one example of an embodiment of timing for a balancedload of ACK/NACK bits and other options exist. In accordance with theexample of Table 5, the TDD uplink subframe n is associated with an FDDdownlink subframe n−k_(i), i=0 to M−1. The TDD uplink subframe n is usedto convey ACK/NACK bits.

The embodiment of Table 5 ensures that each subframe in an FDD frame canalways be associated with an uplink subframe of the TDD carrier with allexisting TDD uplink/downlink configurations and that the processingdelay allowance of four subframes is maintained.

Scheduling Embodiments

Due to the lack of PDCCH subframes in the TDD radio frame, some PDSCHand PUSCH frames may not be able to be scheduled by cross-carrierscheduling from the TDD carrier using current techniques. Thus, in theembodiments below, the ability to schedule every uplink and downlinksubframe on an FDD carrier when a TDD carrier is configured to crosscarrier schedule the FDD carrier are provided.

In a first embodiment, multi-subframe scheduling is provided.Multi-subframe scheduling is used to schedule multiple subframes via asingle PDCCH. This is applicable to both downlink and uplink subframes.

Reference is now made to FIG. 14, which provides a block diagram showinga TDD PCell 1410 and an FDD secondary cell 1420. In the embodiment ofFIG. 14, the special cells are considered to be downlink cells and canbe used to schedule multiple FDD subframes.

In particular, TDD PCell 1410 has TDD configuration 1 and thus subframe0 is a downlink subframe, subframe 1 is a special subframe and subframes2 and 3 are uplink subframes.

In accordance with the embodiment of FIG. 14, as shown by arrows 1430,subframes 2 and 3 of the FDD downlink are scheduled by subframe 1 on theTDD carrier. Similarly, subframes 7 and 8 of the FDD downlink may bescheduled by subframe 6 from the TDD carrier. In this way, all downlinksubframes in the FDD carrier can be scheduled.

Multiple cross-carrier scheduling may be realized through theinteraction of a bitmap field in existing PDSCH assignment DCIs torepresent the number of PDSCH assignments and the position of theseassignments. For example, reference is now made to FIG. 15, which showsa bitmap having four bits. In particular, bitmap 1510 includes bits1512, 1514, 1516 and 1518.

From Table 1 above, the highest number of multiple PDSCH cross-carrierscheduling required is 4 since the maximum number of consecutive uplinksubframes is 3 plus the current subframes. In this case, a four bitbitmap field is used to deal with all scenarios. In the bitmap a “1” mayrepresent the PDSCH assignment presence at the subframe location and a“0” may indicate an absence of an assignment at that location.

In one embodiment bit 1512 may represent the current subframe and the 3bits next to the bit 1512 are used for subsequent future subframes.

If, with certain TDD configurations, the number of downlink PDSCHs whichrequire multiple PDSCH scheduling is less than 4, in one embodiment onlythe number of bits starting from the left hand side which equal to thenumber of possible PDSCH subframes in the TDD configuration are used.Since the UE knows the current TDD configuration, it is able todetermine where the meaningful bits in the four bit bitmap field are.

For example, as shown in FIG. 14, the UE decodes a PDCCH at subframe 1of the TDD carrier for possible PDSCH assignments of FDD carrier atsubframes 1, 2 and 3. Since the UE knows the uplink/downlink TDDconfiguration, it only reads three bits from the left hand side of thebitmap of FIG. 15 to determine the intended PDSCH assignment subframes.

For example if the bitmap field is [1,0,1,0], then the UE knows that thelast bit of the right hand side bears no meaning and would interpret thecurrent DCI containing the PDSCH assignments for subframes 1 and 3.

In a further embodiment, instead of a fixed length of the bitmap, the UEand the eNB may adopt the correct size bit field according to the numberof subframes required to be scheduled by multi-subframe scheduling. Thisis TDD uplink/downlink configuration dependent.

In yet a further embodiment, the redundant bits can be considered torefer to the next available downlink subframe. In this case, even thoughthe downlink subframe may be scheduled in the current subframe, it mayalso have been scheduled in a previous downlink subframe. In this case,the previous configuration may be overridden by the currentconfiguration in some cases.

In a further embodiment, if multiple PDSCH scheduling is always done ina consecutive fashion, two new fields may be introduced in the existingPDSCH assignment DCI. One field may be the number of subframe fieldswhich represents the number of PDSCH subframes being scheduled. This mayrequire 2 bits. The other field is the subframe offset which indicatesthe start point of the subframe being scheduled. This field also needs 2bits.

With regard to existing parts of the DCI content, the HARQ informationand Redundancy Version (RV) fields may be expanded into (1, N) arrays,where N is the number of subframes being scheduled in the DCI. Otherfields, such as, radio bearer assignment, modulation and coding scheme(MCS), among others, may remain the same as in the currentspecification. All scheduled subframes can use the same resource block(RB) and modulation scheme.

In a further embodiment, the resource allocation for multiple subframesmay be different. The DCI content may include all the different resourceallocations, and for each allocation an offset field may be included toindicate which subframe is being allocated with the current subframe asthe reference point. For example, the offset field could be two bits,which could indicate at most four future subframes. In anotherembodiment, the resource allocation for all the indicated subframes maybe identical. In this case, only the subframe index may need to beincluded.

Multiple PUSCH Scheduling

For PUSCH transmission, because of the synchronous HARQ, HARQ, timing isharder to design, especially when the scheduling cell is TDD whichusually does not have enough downlink subframes to cross-carrierschedule all uplink subframes in the FDD SCell. One further designconsideration is to keep the synchronous nature of uplink HARQ.

Therefore, in accordance with one embodiment of the present disclosure,the timing scheme for the PUSCH transmission is illustrated with regardto FIG. 16.

As seen in FIG. 16, the PCell is a TDD configuration 1 cell and is shownwith reference 1610. The secondary cell is shown with reference 1620 andis an FDD uplink carrier.

As seen in FIG. 16, a unified timing linkage scheme is provided. Thescheme can be applied to any TDD uplink/downlink configuration when thescheduling cell is TDD and cross-carrier schedule uplink subframes in anFDD cell. This is because all scheduling grants and ACK/NACK bittransmissions are from subframes 0, 1, 5 and 6, which are alwaysdownlink, regardless of the TDD configuration.

With the timing scheme, the synchronous nature of uplink HARQ ismaintained. The HARQ round trip time (RTT) of most subframes is 10 ms,except for subframes 3 and 8 which have a 20 ms round trip time. Thismay require 10 HARQ processes on the FDD uplink. The process ID has aone-to-one mapping with the subframe number and is given by equation 1below.UL HARQ Process ID=(SFN×10+subframe)mod 10  (1)

Based on equation 1 above, the subframe number implicitly represents theuplink HARQ process identifier.

With regard to scheduling, as shown by the arrows in FIG. 16, the timingscheme uses one downlink subframe to schedule multiple uplink subframePUSCHs. For example, subframe 1 on the TDD cell may schedule subframes5, 6, 7 and 8 on the FDD SCell uplink.

Similar to multiple PDSCH scheduling described above, the multiple PUSCHscheduling may be realized by introducing a bitmap field in existingPUSCH grant DCI to represent the number of PUSCH grants and the positionof these uplink grants. As seen in FIG. 16, the most number of multiplePUSCH cross-carrier scheduling required is 4. Therefore, a 4-bit bitmapfield may be used to provide for all possible scenarios. In oneembodiment, a “1” may represent the PUSCH grant presence at the subframelocation and a “0” may represent the absence of a grant at thatlocation. In one embodiment, the most left hand side bit may representthe ‘current plus four’ subframe, and the three bits next to it are forsubsequent future subframes.

Alternatively, if the multiple PUSCH scheduling is always done in aconsecutive fashion, two new fields may be introduced in the existingPUSCH grant DCI. One is called the number of subframes field, whichrepresents the number of PUSCH subframes being scheduled. In oneexample, this may be a 2 bit field because of the maximum number ofmultiple subframes is 4.

The other field is the subframe offset which indicates the start pointof the subframe being scheduled. In other example, this field may use 2bits as well. Other numbers of bits however may also be possible.

The HARQ process ID is implicitly indicated via the subframe number, andhence there is no need to communicate it in the PUSCH grant. Moreover,the process in a non-adaptive uplink HARQ process and the RV isdetermined through a predefined sequence, as specified in the 3GPPTS36.321 specification.

In an alternative embodiment, the uplink subframes 3 and 8 may be leftunscheduled. In this way, the number of uplink HARQ processes requiredfor the FDD carrier is 8, which are the same as in the standalone FDDcarrier. Moreover, all of the HARQ round trip times would be the same at10 ms in this case.

Cross-Subframe Scheduling

Further, the multi-subframe scheduling can improve the ability tocross-carrier schedule subframes on the FDD carrier from the TDDcarrier. However, these multiple subframe assignments need to bedirected to the same UE. In order to introduce more flexibility,cross-subframe scheduling is proposed.

In particular, in this embodiment, an index which indicates the subframepositions of downlink assignments or uplink grants is added to thecorresponding DCI payload. Similar to the above embodiments, the maximumnumber of subframes to schedule is four. In this case, a two-bit indexmay be used to cope with all the possible scenarios. Table 6 below givesan example of downlink subframe position mapping indexes inserted intoexisting downlink assignment DCIs.

TABLE 6 DL subframe position index b₁b₀ subframe position 00 current DLsubframe on FDD carrier 01 1^(st) subsequent DL subframe on FDD carrier10 2^(nd) subsequent DL subframe on FDD carrier 11 3^(rd) subsequent DLsubframe on FDD carrier

Table 7 shows uplink subframe position mapping indexes inserted into theexisting DCI 0/DCI 4.

TABLE 7 UL subframe position index b₁b₀ subframe position 00 currentsubframe + 4 on UL FDD carrier 01 1^(st) subsequent UL subframe on FDDcarrier 10 2^(nd) subsequent UL subframe on FDD carrier 11 3^(rd)subsequent UL subframe on FDD carrier

Tables 6 and 7 provide for cross subframe scheduling by providing thesubframe position index for both the uplink and downlink.

The HARQ operations will need to be recognized by the network and inparticular by a network element such as an eNB. A simplified networkelement is shown with regard to FIG. 17.

In FIG. 17, network element 1710 includes a processor 1720 and acommunications subsystem 1730, where the processor 1720 andcommunications subsystem 1730 cooperate to perform the methods describedabove.

Further, the above may be implemented by any UE. One exemplary device isdescribed below with regard to FIG. 18.

UE 1800 is typically a two-way wireless communication device havingvoice and data communication capabilities. UE 1800 generally has thecapability to communicate with other computer systems. Depending on theexact functionality provided, the UE may be referred to as a datamessaging device, a two-way pager, a wireless e-mail device, a cellulartelephone with data messaging capabilities, a wireless Internetappliance, a wireless device, a mobile device, or a data communicationdevice, as examples.

Where UE 1800 is enabled for two-way communication, it may incorporate acommunication subsystem 1811, including both a receiver 1812 and atransmitter 1814, as well as associated components such as one or moreantenna elements 1816 and 1818, local oscillators (LOs) 1813, and aprocessing module such as a digital signal processor (DSP) 1820. As willbe apparent to those skilled in the field of communications, theparticular design of the communication subsystem 1811 will be dependentupon the communication network in which the device is intended tooperate. The radio frequency front end of communication subsystem 1811can be any of the embodiments described above.

Network access requirements will also vary depending upon the type ofnetwork 1819. In some networks network access is associated with asubscriber or user of UE 1800. A UE may require a removable useridentity module (RUIM) or a subscriber identity module (SIM) card inorder to operate on a network. The SIM/RUIM interface 1844 is normallysimilar to a card-slot into which a SIM/RUIM card can be inserted andejected. The SIM/RUIM card can have memory and hold many keyconfigurations 1851, and other information 1853 such as identification,and subscriber related information.

When required network registration or activation procedures have beencompleted, UE 1800 may send and receive communication signals over thenetwork 1819. As illustrated in FIG. 18, network 1819 can consist ofmultiple base stations communicating with the UE.

Signals received by antenna 1816 through communication network 1819 areinput to receiver 1812, which may perform such common receiver functionsas signal amplification, frequency down conversion, filtering, channelselection and the like. A/D conversion of a received signal allows morecomplex communication functions such as demodulation and decoding to beperformed in the DSP 1820. In a similar manner, signals to betransmitted are processed, including modulation and encoding forexample, by DSP 1820 and input to transmitter 1814 for digital to analogconversion, frequency up conversion, filtering, amplification andtransmission over the communication network 1819 via antenna 1818. DSP1820 not only processes communication signals, but also provides forreceiver and transmitter control. For example, the gains applied tocommunication signals in receiver 1812 and transmitter 1814 may beadaptively controlled through automatic gain control algorithmsimplemented in DSP 1820.

UE 1800 generally includes a processor 1838 which controls the overalloperation of the device. Communication functions, including data andvoice communications, are performed through communication subsystem1811. Processor 1838 also interacts with further device subsystems suchas the display 1822, flash memory 1824, random access memory (RAM) 1826,auxiliary input/output (I/O) subsystems 1828, serial port 1830, one ormore keyboards or keypads 1832, speaker 1834, microphone 1836, othercommunication subsystem 1840 such as a short-range communicationssubsystem and any other device subsystems generally designated as 1842.Serial port 1830 could include a USB port or other port known to thosein the art.

Some of the subsystems shown in FIG. 18 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as keyboard 1832 and display1822, for example, may be used for both communication-related functions,such as entering a text message for transmission over a communicationnetwork, and device-resident functions such as a calculator or tasklist.

Operating system software used by the processor 1838 may be stored in apersistent store such as flash memory 1824, which may instead be aread-only memory (ROM) or similar storage element (not shown). Thoseskilled in the art will appreciate that the operating system, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile memory such as RAM 1826. Received communication signals mayalso be stored in RAM 1826.

As shown, flash memory 1824 can be segregated into different areas forboth computer programs 1858 and program data storage 1850, 1852, 1854and 1856. These different storage types indicate that each program canallocate a portion of flash memory 1824 for their own data storagerequirements. Processor 1838, in addition to its operating systemfunctions, may enable execution of software applications on the UE. Apredetermined set of applications that control basic operations,including at least data and voice communication applications forexample, will normally be installed on UE 1800 during manufacturing.Other applications could be installed subsequently or dynamically.

Applications and software may be stored on any computer readable storagemedium. The computer readable storage medium may be a tangible or intransitory/non-transitory medium such as optical (e.g., CD, DVD, etc.),magnetic (e.g., tape) or other memory known in the art.

One software application may be a personal information manager (PIM)application having the ability to organize and manage data itemsrelating to the user of the UE such as, but not limited to, e-mail,calendar events, voice mails, appointments, and task items. Naturally,one or more memory stores would be available on the UE to facilitatestorage of PIM data items. Such PIM application may have the ability tosend and receive data items, via the wireless network 1819. Furtherapplications may also be loaded onto the UE 1800 through the network1819, an auxiliary I/O subsystem 1828, serial port 1830, short-rangecommunications subsystem 1840 or any other suitable subsystem 1842, andinstalled by a user in the RAM 1826 or a non-volatile store (not shown)for execution by the processor 1838. Such flexibility in applicationinstallation increases the functionality of the device and may provideenhanced on-device functions, communication-related functions, or both.For example, secure communication applications may enable electroniccommerce functions and other such financial transactions to be performedusing the UE 1800.

In a data communication mode, a received signal such as a text messageor web page download will be processed by the communication subsystem1811 and input to the processor 1838, which may further process thereceived signal for output to the display 1822, or alternatively to anauxiliary I/O device 1828.

A user of UE 1800 may also compose data items such as email messages forexample, using the keyboard 1832, which may be a complete alphanumerickeyboard or telephone-type keypad, among others, in conjunction with thedisplay 1822 and possibly an auxiliary I/O device 1828. Such composeditems may then be transmitted over a communication network through thecommunication subsystem 1811.

For voice communications, overall operation of UE 1800 is similar,except that received signals would typically be output to a speaker 1834and signals for transmission would be generated by a microphone 1836.Alternative voice or audio I/O subsystems, such as a voice messagerecording subsystem, may also be implemented on UE 1800. Although voiceor audio signal output is generally accomplished primarily through thespeaker 1834, display 1822 may also be used to provide an indication ofthe identity of a calling party, the duration of a voice call, or othervoice call related information for example.

Serial port 1830 in FIG. 18 would normally be implemented in a personaldigital assistant (PDA)-type UE for which synchronization with a user'sdesktop computer (not shown) may be desirable, but is an optional devicecomponent. Such a port 1830 would enable a user to set preferencesthrough an external device or software application and would extend thecapabilities of UE 1800 by providing for information or softwaredownloads to UE 1800 other than through a wireless communicationnetwork. The alternate download path may for example be used to load anencryption key onto the device through a direct and thus reliable andtrusted connection to thereby enable secure device communication. Aswill be appreciated by those skilled in the art, serial port 1830 canfurther be used to connect the UE to a computer to act as a modem.

Other communications subsystems 1840, such as a short-rangecommunications subsystem, is a further optional component which mayprovide for communication between UE 1800 and different systems ordevices, which need not necessarily be similar devices. For example, thesubsystem 1840 may include an infrared device and associated circuitsand components or a Bluetooth™ communication module to provide forcommunication with similarly enabled systems and devices. Subsystem 1840may further include non-cellular communications such as WiFi, WiMAX, ornear field communications (NFC).

The embodiments described herein are examples of structures, systems ormethods having elements corresponding to elements of the techniques ofthis application. This written description may enable those skilled inthe art to make and use embodiments having alternative elements thatlikewise correspond to the elements of the techniques of thisapplication. The intended scope of the techniques of this applicationthus includes other structures, systems or methods that do not differfrom the techniques of this application as described herein, and furtherincludes other structures, systems or methods with insubstantialdifferences from the techniques of this application as described herein.Further, various embodiments are shown with regards to the clausesbelow:

AA. A method at a user equipment for hybrid automatic repeat request(HARQ) operation, the user equipment operating on a primary carrierhaving a first duplex mode and on at least one secondary carrier havinga second duplex mode, the method comprising: using HARQ timing operationof a predetermined configuration of the first duplex mode for the atleast one secondary carrier, wherein the predetermined configuration isused regardless of the configuration of the first duplex mode on theprimary carrier.

BB. The method of clause AA, wherein the first duplex mode is timedivision duplex (TDD).

CC. The method of clause BB, wherein the predetermined configuration ischosen based on the periodicity of the primary carrier.

DD. The method of clause CC, wherein the predetermined configuration isTDD configuration 2 physical downlink shared channel (PDSCH) timing fora 5 ms periodicity and TDD configuration 5 PDSCH timing for a 10 msperiodicity.

EE. The method of clause AA, wherein the predetermined configuration isTDD configuration 5 physical downlink shared channel (PDSCH) timing.

FF. A user equipment for hybrid automatic repeat request (HARQ)operation, the user equipment operating on a primary carrier having afirst duplex mode and on at least one secondary carrier having a secondduplex mode, the user equipment comprising a processor configured to:use HARQ timing operation of a predetermined configuration of the firstduplex mode for the at least one secondary carrier, wherein thepredetermined configuration is used regardless of the configuration ofthe first duplex mode on the primary carrier.

GG. The user equipment of clause FF, wherein the first duplex mode istime division duplex (TDD).

HH. The user equipment of clause GG, wherein the predeterminedconfiguration is chosen based on the periodicity of the primary carrier.

II. The user equipment of clause HH, wherein the predeterminedconfiguration is TDD configuration 2 physical downlink shared channel(PDSCH) timing for a 5 ms periodicity and TDD configuration 5 PDSCHtiming for a 10 ms periodicity.

JJ. The user equipment of clause FF, wherein the predeterminedconfiguration is TDD configuration 5 physical downlink shared channel(PDSCH) timing.

KK. A method at a user equipment for hybrid automatic repeat request(HARQ) operation, the user equipment operating on a primary carrierhaving a first duplex mode and on at least one secondary carrier havinga second duplex mode, the method comprising: utilizing an availableuplink subframe after a predetermined processing delay on the primarycarrier for acknowledgement of a subframe on the secondary carrier.

LL. The method of clause KK, wherein the available uplink subframe is anext available uplink subframe after the predetermined processing delay.

MM. The method of clause KK., wherein the predetermined processing delayis four subframes.

NN. The method of clause KK, wherein the available uplink subframe isdetermined based on a lookup table.

OO. The method of clause NN, wherein the lookup table distributesacknowledgements between uplink subframes on the primary carrier.

PP. The method of clause NN, wherein the lookup table ensures eachsubframe on the secondary carrier is associated with an uplink subframe.

QQ. A user equipment for hybrid automatic repeat request (HARQ)operation, the user equipment operating on a primary carrier having afirst duplex mode and on at least one secondary carrier having a secondduplex mode, the user equipment comprising a processor configured to:use an available uplink subframe after a predetermined processing delayon the primary carrier for acknowledgement of a subframe on thesecondary carrier.

RR. The user equipment of clause QQ, wherein the available uplinksubframe is a next available uplink subframe after the predeterminedprocessing delay.

SS. The user equipment of clause QQ, wherein the predeterminedprocessing delay is four subframes.

TT. The user equipment of clause QQ, wherein the available uplinksubframe is determined based on a lookup table.

UU. The user equipment of clause TT, wherein the lookup tabledistributes acknowledgements between uplink subframes on the primarycarrier.

VV. The user equipment of clause TT, wherein the lookup table ensureseach subframe on the secondary carrier is associated with an uplinksubframe.

WW. A method at a user equipment for downlink cross-carrier schedulingat least one secondary carrier having a second duplex mode using aprimary carrier having a first duplex mode, the method comprising:receiving downlink scheduling information from a network element, thedownlink scheduling information including scheduling for a currentsubframe and future subframes on the secondary carrier; and receivingdata on the secondary carrier based on the downlink schedulinginformation.

XX. The method of clause WW, wherein the downlink scheduling informationis received as part of a downlink control information assignment.

YY. The method of clause XX, wherein the downlink scheduling informationis received as a bitmap.

ZZ. The method of clause YY, wherein the bitmap is of fixed size toschedule a current subframe and a maximum number of future subframes.

AAA. The method of clause ZZ, wherein the maximum number of subframes isdetermined based on a long term evolution time division duplexconfiguration.

BBB. The method of clause AAA, wherein, if not all bits in the bitmapare needed for scheduling, the unneeded bits are ignored by the userequipment.

CCC. The method of clause AAA, wherein if not all bits in the bitmap areneeded for scheduling, the bitmap includes redundant scheduling forfuture subframes.

DDD. The method of clause YY, wherein the bitmap is of variable lengthbased on a number of subframes being scheduled.

EEE. The method of clause XX, wherein the downlink schedulinginformation includes a first field to indicate a number of subframesbeing scheduled and a second field to indicate an offset for ascheduling start point.

FFF. A user equipment for downlink cross-carrier scheduling at least onesecondary carrier having a second duplex mode using a primary carrierhaving a first duplex mode, the user equipment comprising a processorconfigured to: receive downlink scheduling information from a networkelement, the downlink scheduling information including scheduling for acurrent subframe and future subframes on the secondary carrier; andreceive data on the secondary carrier based on the downlink schedulinginformation.

GGG. The user equipment of clause FFF, wherein the downlink schedulinginformation is received as part of a downlink control informationassignment.

HHH. The user equipment of clause GGG, wherein the downlink schedulinginformation is received as a bitmap.

III. The user equipment of clause HHH, wherein the bitmap is of fixedsize to schedule a current subframe and a maximum number of futuresubframes.

JJJ. The user equipment of clause Ill, wherein the maximum number ofsubframes is determined based on a long term evolution time divisionduplex configuration.

KKK. The user equipment of clause JJJ, wherein, if not all bits in thebitmap are needed for scheduling, the unneeded bits are ignored by theuser equipment.

LLL. The user equipment of clause JJJ, wherein if not all bits in thebitmap are needed for scheduling, the bitmap includes redundantscheduling for future subframes.

MMM. The user equipment of clause HHH, wherein the bitmap is of variablelength based on a number of subframes being scheduled.

NNN. The user equipment of clause Ill, wherein the downlink schedulinginformation includes a first field to indicate a number of subframesbeing scheduled and a second field to indicate an offset for ascheduling start point.

NNN. A method at a user equipment for uplink cross-carrier scheduling atleast one secondary carrier having a frequency division duplex (FDD)mode using a primary carrier having time division duplex (TDD) mode, themethod comprising: utilizing a subset of subframes for uplink schedulingof the at least one secondary carrier, wherein the subset of subframesare downlink subframes in all TDD configurations; and receivingacknowledgments on the subset of subframes, wherein the acknowledgmentsare received on the same subframe number as the subframe used for uplinkscheduling.

OOO. The method of clause NNN, wherein the subframes for uplinkscheduling are used to schedule multiple uplink subframes on thesecondary carrier.

PPP. The method of clause OOO, wherein the scheduling information isreceived in a bitmap in a downlink control information grant.

QQQ. The method of clause OOO, wherein the scheduling information isreceived in at least two fields in a downlink control information grant,a first field indicating a number of subframes to be scheduled and asecond field indicating a subframe offset.

RRR. The method of clause NNN, wherein the subset of subframes aresubframes 0, 1, 5 and 6.

SSS. A user equipment for uplink cross-carrier scheduling at least onesecondary carrier having a frequency division duplex (FDD) mode using aprimary carrier having time division duplex (TDD) mode, the userequipment comprising a processor configured to: utilize a subset ofsubframes for uplink scheduling of the at least one secondary carrier,wherein the subset of subframes are downlink subframes in all TDDconfigurations; and receive acknowledgments on the subset of subframes,wherein the acknowledgments are received on the same subframe number asthe subframe used for uplink scheduling.

TTT. The user equipment of clause SSS, wherein the subframes for uplinkscheduling are used to schedule multiple uplink subframes on thesecondary carrier.

UUU. The user equipment of clause TTT, wherein the schedulinginformation is received in a bitmap in a downlink control informationgrant.

VVV. The user equipment of clause TTT, wherein the schedulinginformation is received in at least two fields in a downlink controlinformation grant, a first field indicating a number of subframes to bescheduled and a second field indicating a subframe offset.

WWW. The user equipment of clause SSS, wherein the subset of subframesare subframes 0, 1, 5 and 6.

The invention claimed is:
 1. A method, at a user equipment for subframescheduling operation, the user equipment operating on a primary carrierhaving a time division duplex (TDD) mode and at least one secondarycarrier having a frequency division duplex (FDD) mode, the methodcomprising: receiving on the primary carrier a Downlink ControlInformation (DCI) on a Physical Downlink Control Channel (PDCCH), theDCI comprising an assignment bitmap for the secondary carrier, whereineach bit in the assignment bitmap corresponds to a subframe, and whereina value of each bit indicates whether the corresponding subframe isscheduled; determining a plurality of subframes from the assignmentbitmap; scheduling on the secondary carrier the subframes determinedfrom the assignment bitmap; wherein the assignment bitmap comprises anumber of bits equal to a number of consecutive uplink subframes of aTDD configuration of the primary carrier following a current subframeplus one.
 2. The method of claim 1, wherein only a subset of bits of theassignment bitmap are used, the subset being selected based on a TDDconfiguration of the primary carrier and a current subframe.
 3. Themethod of claim 2, wherein the subset comprises a number of bits equalto a number of consecutive uplink subframes of the TDD configurationfollowing the current subframe plus one.
 4. The method of claim 3,wherein bits of the assignment bitmap which are not in the subsetinclude scheduling information for a next available downlink subframe.5. The method of claim 1, wherein the assignment bitmap comprises afirst field indicating a number of subframes and a second fieldindicating a subframe offset, and wherein the scheduling comprisesscheduling the number of consecutive subframes starting from theindicated subframe offset.
 6. The method of claim 1, further comprisinga plurality of resource allocations, each resource allocation comprisingan offset field indicating a subframe based on a current subframe. 7.The method of claim 1, wherein the scheduled subframes are uplinksubframes.
 8. The method of claim 7, wherein a Hybrid Automatic RepeatreQuest (HARD) process identifier for each scheduled subframe isdetermined from a subframe number.
 9. The method of claim 1, wherein theassignment bitmap comprises an index which maps to a subframe positionrelative to a current subframe.
 10. A user equipment operating on aprimary carrier having a time division duplex (TDD) mode and at leastone secondary carrier having a frequency division duplex (FDD) mode, theuser equipment comprising: a processor; and a communications subsystem;wherein the processor and communication subsystem cooperate to: receiveon the primary carrier a Downlink Control Information (DCI) on aPhysical Downlink Control Channel (PDCCH), the DCI comprising anassignment bitmap for the secondary carrier, wherein each bit in theassignment bitmap corresponds to a subframe, and wherein a value of eachbit indicates whether the corresponding subframe is scheduled; determinea plurality of subframes from the assignment bitmap; schedule on thesecondary carrier the subframes determined from the assignment bitmap;wherein the assignment bitmap comprises a number of bits equal to anumber of consecutive uplink subframes of a TDD configuration of theprimary carrier following a current subframe plus one.
 11. The userequipment of claim 10, wherein only a subset of bits of the assignmentbitmap are used, the subset comprising a number of bits equal to anumber of consecutive uplink subframes of the TDD configurationfollowing the current subframe plus one.
 12. The user equipment of claim11, wherein bits of the assignment bitmap which are not in the subsetinclude scheduling information for a next available downlink subframe.13. The user equipment of claim 10, wherein the assignment bitmapcomprises a first field indicating a number of subframes and a secondfield indicating a subframe offset, and wherein the scheduling comprisesscheduling the number of consecutive subframes starting from theindicated subframe offset.
 14. The user equipment of claim 10, whereinthe assignment bitmap comprises a plurality of resource allocations,each resource allocation comprising an offset field indicating asubframe based on a current subframe.
 15. The user equipment of claim10, wherein the scheduled subframes are uplink subframes.
 16. The userequipment of claim 10, wherein a Hybrid Automatic Repeat reQuest (HARQ)process identifier for each scheduled subframe is determined from asubframe number.